How to make your custom domain of blogspot blog access with domain or naked domain:

Optional: You can also enter A-records,
which links your naked domain (example.com) to an actual site
(www.example.com). If you skip this step, visitors who leave off the
"www" will see an error page.

Optional continued: After completing Step
8, enter your domain name in the format example.com, and list the I.P.
addresses shown below in the "A" section. You'll need to create four
separate A-records which point to four different Google IPs.
216.239.32.21
216.239.34.21
216.239.36.21
216.239.38.21End of optional section

But only completing step 1, that is not enough:Step2: Enable redirect naked domain to domain.

Go to blogger settings: enabled the "Redirect yourdomain.com to www.yourdomain.com."